As a follow up to my last post – the following extension methods make it easy to manually serialize claim sets:

public static XElement Serialize(
  this ClaimSet set, IEnumerable<Type> knownTypes)
{
    DataContractSerializer dcs = new DataContractSerializer(
        set.GetType(),
        knownTypes,
        int.MaxValue,
        false,
        true,
        null);
   
    MemoryStream ms = new MemoryStream();
    dcs.WriteObject(ms, set);
    ms.Seek(0, SeekOrigin.Begin);
   
    return XElement.Load(new XmlTextReader(ms));
}

public static XElement Serialize(
  this IEnumerable<ClaimSet> claimSets, string rootName,
  string rootNamespace, IEnumerable<Type> knownTypes)
{
    XNamespace ns = XNamespace.Get(rootNamespace);

    return new XElement(ns + rootName,
                    from cs in claimSets
                    select cs.Serialize(knownTypes));
}